J/MNRAS/496/3469 VLA imaging of the XMM-LSS/VIDEO deep field (Heywood+, 2020)
VLA imaging of the XMM-LSS/VIDEO deep field at 1-2 GHz.
Heywood I., Hale C.L., Jarvis M.J., Makhathini S., Peters J.A.,
Sebokolodi M.L.L., Smirnov O.M.
<Mon. Not. R. Astron. Soc., 496, 3469-3481 (2020)>
=2020MNRAS.496.3469H 2020MNRAS.496.3469H (SIMBAD/NED BibCode)
ADC_Keywords: Radio sources ; Interferometry ; Positional data
Keywords: techniques: interferometric - radio continuum: galaxies
Abstract:
Modern radio telescopes are routinely reaching depths where normal
star-forming galaxies are the dominant observed population. Realizing
the potential of radio as a tracer of star formation and black hole
activity over cosmic time involves achieving such depths over
representative volumes, with radio forming part of a larger
multiwavelength campaign. In pursuit of this, we used the Karl G.
Jansky Very Large Array (VLA) to image ∼5deg2 of the VIDEO/XMM-LSS
extragalactic deep field at 1-2GHz. We achieve a median depth of
16uJy/beam with an angular resolution of 4.5arcsec. Comparisons with
existing radio observations of XMM-LSS showcase the improved survey
speed of the upgraded VLA: we cover 2.5 times the area and increase
the depth by ∼20 per cent in 40 per cent of the time.
Direction-dependent calibration and wide-field imaging were required
to suppress the error patterns from off-axis sources of even modest
brightness. We derive a catalogue containing 5762 sources from the
final mosaic. Sub-band imaging provides in-band spectral indices for
3458 (60 per cent) sources, with the average spectrum becoming flatter
than the canonical synchrotron slope below 1mJy. Positional and flux
density accuracy of the observations, and the differential source
counts are in excellent agreement with those of existing measurements.
A public release of the images and catalogue accompanies this article.
Description:
The observations were conducted using the VLA in B-configuration. A
single 1.5h Scheduling Block (SB) was submitted for each of the 32
pointings, containing the necessary calibrator scans, as well as scans
of the science target. The on-source observation time for each target
pointing was 67.5m, with 3s per correlator integration. The correlator
was configured in standard wide-band continuum mode, with
0.994-2.018GHz of spectral coverage split up into 16MHzx64MHz spectral
windows (SPWs) for a total of 1024 channels.
The package PROFOUND (Robotham et al. 2018MNRAS.476.3137R 2018MNRAS.476.3137R) was used to
generate an associated source catalogue from the total intensity
mosaic. Although designed for optical/near-infrared surveys, PROFOUND
has been shown to be able to successfully model radio emission (Hale
et al. 2019MNRAS.487.3971H 2019MNRAS.487.3971H) for sources of different morphologies. As
PROFOUND does attempt to fit to any particular morphology (e.g. 2D
Gaussians), complex morphologies (e.g. AGNs with extended jets) may be
more faithfully modelled.
Using PROFOUND we derived a catalogue containing 5762 sources from the
total intensity mosaic. The properties of our final sample of radio
sources are shown in Table 1.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 190 5762 Radio source catalogue
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- ID Radio source identifier
(JHHMMSS.ss+DDMMSS.s)
21- 28 F8.5 deg RAdeg Right ascension (J2000) (1)
30- 37 F8.5 deg DEdeg Declination (J2000) (1)
39- 43 F5.2 arcsec e_RAdeg Error on RAdeg (2)
45- 49 F5.2 arcsec e_DEdeg Error on DEdeg (2)
51- 58 F8.5 deg RApeak Right ascension of the peak (J2000) (3)
60- 67 F8.5 deg DEpeak Declination of the peak (J2000) (3)
69- 77 F9.5 mJy Sint Integrated flux density (4)
79- 85 F7.5 mJy e_Sint Error on Sint
87- 95 F9.5 mJy/beam Speak Peak intensity (5)
97- 103 F7.5 mJy/beam e_Speak Error on Speak
105- 111 F7.5 mJy/beam rmspeak Root-mean square value in the map at the
peak position of the source
113- 119 F7.5 mJy/beam e_rmspeak Error on rmspeak
121- 126 F6.2 arcsec thetamaj Major axis size of the segment (6)
128- 132 F5.2 arcsec thetamin Minor axis size of the segment (7)
134- 139 F6.2 deg PA Position angle of the source
141- 145 F5.2 --- alpha ? Spectral index (8)
147- 150 F4.2 --- e_alpha ? Error on alpha
152- 170 A19 --- ID2 Second IAU source identifier
172- 190 A19 --- ID3 Third IAU source identifier
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Note (1): Flux-weighted right ascension and declination of the component in
degrees taken from the RAcen and Deccen columns from PROFOUND
Note (2): Flux-weighted standard deviations in the right ascension and
declination of the component, taken from the xsd and ysd columns from
PROFOUND and converted into angular units using the pixel sizes. Note
that this is significantly larger than the statistical uncertainty
that can be obtained by fitting a point or Gaussian component, and is
included here mainly for completeness.
Note (3): Right ascension and declination of the peak of the source in degrees
taken from the RAmax and Decmax columns from PROFOUND
Note (4): Integrated flux density of the component in mJy. This is calculated
using the PROFOUND flux column, converted to Jy (from Jy/beam), with
an appropriate beam correction applied to compensate for the flux
density contribution from the outer wings of the emission.
Note (5): Peak intensity of the component in mJy/beam. This is constructed from
the PROFOUND catalogue as flux x cenfrac.
Note (6): Major axis size of the segment and is quoted here as the 2xR100 column
from PROFOUND and converted to arcseconds
Note (7): Minor axis size of the segment and is quoted here as the 2xR100xaxrat
from PROFOUND and converted to arcseconds
Note (8): Spectral index estimate formed by extracting pixels from the spectral
index map over the region corresponding to a given source as
determined by PROFOUND. The mean of the spectral index value of the
extracted pixels is determined, weighted by the total intensity values
over the same area.
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 05-Jul-2023